The project will deal with the development of psychophysical procedures to assess olfaction in clinical patients. It will scrutinize, build upon, and extend procedures previously developed at the Connecticut Chemosensory Clinical Research Center (CCCRC). The first part of the project will address issues of olfactory and trigeminal sensitivity in normal persons and in persons previously found to be hyposmic or anosmic. One experiment will chart sensitivity to four odorants in order to decide whether or not only one odorant will suffice to gauge sensitivity clinically. Another experiment will examine the distribution of both the absolute threshold for nasal irritation and sensitivity to a reflex (transitory apnea) triggered by irritation. Knowledge of sensitivity to irritation can help decide whether olfactory deficits are sometimes accompanied by deficits of the common chemical sense. The current psychophysical procedures of the CCCRC will receive attention in tests of reliability and in comparisons among the CCCRC tests and those used in other clinics. The research will extend to means of diagnosing types of hyposmia, parosmia, and malingering. Specific experiments here will address the relation between threshold and supra-threshold intensity perception in normal and hyposmic persons; quality discrimination and identification of odorous substances on both the inhalation and exhalation phases of the breathing cycle in normal, hyposmic, and parosmic persons; and smell-taste confusions in normal, anosmic, and "malingering" persons. An investigation of how odor quality discrimination and odor identification vary with perceived intensity will provide information on the means to choose items for clinical tests of odor identification and will provide a theoretical rationale for such tests.